Data not posting to NextJS API Route

I have a simple form on a NextJS page, with the data stored in state:

const [bookingInfo, setBookingInfo] = useState({
    name: "",
    email: "",
    phone: "",
  });

const handleChange = (e) => {
    setBookingInfo({ ...bookingInfo, [e.target.name]: e.target.value });
 };

<form onSubmit={handleSubmit} className="flex-col">
            <input
              type="text"
              name="name"
              value={bookingInfo.name}
              placeholder="name"
              onChange={handleChange}
            />
            <input
              type="text"
              name="email"
              value={bookingInfo.email}
              placeholder="email"
              onChange={handleChange}
            />
            <input
              type="text"
              name="phone"
              value={bookingInfo.phone}
              placeholder="phone"
              onChange={handleChange}
            />
            <button>Submit</button>
          </form>

On submit I’m saving the data in localStorage via a function in my Context (where it shows up perfectly), and sending the data (hopefully) to my API route:

const handleSubmit = async (e) => {
    e.preventDefault();

    saveCustomerDetails(bookingInfo);

    const response = await fetch("/api/checkout", {
      method: "POST",
      headers: { "Content-Type": "application/json" },
      body: JSON.stringify(bookingInfo),
    });

    console.log(response);
  };

All I have in my API route at /api/checkout.js for now is:

export default async function handler(res, req) {
  try {
    console.log(req.body);
  } catch (error) {}
}

However the console logs ‘undefined’, and I get a warning undefined API resolved without sending a response for /api/checkout, this may result in stalled requests. Any ideas what’s going on?

>Solution :

Your API handler has arguments in wrong order – req comes before res. Also you are getting API resolved without sending a response for /api/checkout, this may result in stalled requests. because you are not sending any response with res.

So your code should be:

export default async function handler(req, res) {
  try {
    console.log(req.body);
    res.status(200).json({
       message: 'Success', // just an example
    });
  } catch (error) {}
}